JPH026206A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the rim runout preventing performance by making the ratio (l1/W) of the tire axial distance l1 between the sectional center-of-gravity position of the bead core of a tire and the bead toe to the whole width W of the bead bottom part above 0.5 and less than 0.6. CONSTITUTION:In this invention, the ratio (l1/W) of the tire axial distance l1 between the sectional center-of-gravity position of the bead core 3 of a tire and the bead toe 7 to the whole width of the bead bottom part is above 0.5 and less than 0.6. As a concrete means of obtaining said ratio (l1/W) exceeding 0.5, it is adapted to thin the thickness of a rim cushion (rubber layer) 8. The rim cushion 8 is generally provided on the part contacting with a rim flange, and has a function of protecting a carcass layer 4 from a rubbing damage with the rim. In this invention, by thinning the thickness of the rim cushion layer 8, the ratio l1/W) is made above 0.5 to improve the rim runout preventing property of the tire.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a highly safe pneumatic radial tire (hereinafter referred to as , simply referred to as tires).

[Conventional technology]

Generally, when the air pressure of a tire fitted to a rim decreases, the bead portion of the tire tends to come off from the rim, which is extremely dangerous when driving a vehicle.

There are two ways to prevent this tire from coming off the rim: improving the tire side and improving the rim side.
When improving the tire side, there is a possibility that the tire performance may change, so efforts have usually been made to improve the rim side, which is free from such risks.

The present invention relates to a tire that prevents the rim from coming off.

When considering the fitting between the tire and the rim, for example, in FIG. 2, suppose that a lateral force (lateral pushing force) F shown by an arrow acts on the tire 1 filled with a predetermined internal pressure P.
Without the tire leaking air against this F,
The mechanical balance for maintaining a stable fit with the rim 2 can be expressed by the following equation.

F-12,=f, -It,'+f, ・12...
・・・・・・■F-f, +f, ・・・・・・・・・・・・
...... ■In the above formula, f is the tightening force by the bead core 3 (wire), r2 is the resistance force due to the tire casing such as internal pressure and rigidity around the bead, and 'f is the bead toe 6 due to the hump 9 , lI゛ is the distance in the axial direction of the tire between the cross-sectional center of gravity of the bead core 3 and the bead tow 6 when it is attached to e, 12 is the height from the bead tow 6 to the tire maximum width, and 13 is the distance from the bead tow 6 to the tire maximum width. This is the height to the tread outer peripheral surface T.

From the above formula, it can be seen that the following measures are effective in improving the rim detachability of the tire.

(1) The tightening force f by the bead wire is increased. Specifically, the number of arranged wires, the number of layers, etc. of the bead core is increased, and the cross-sectional area of the bead core is increased.

(2) Increase z+'. That is, in consideration of the moment of the lateral force F, the cross-sectional center of gravity of the bead wire is separated from the bead tow outward in the tire axial direction.

(3) Increase the bead tow reaction force f3 due to the hump. Specifically, the rigidity of the bead toe portion is increased.

(4) Increase lz to make the tire difficult to deform. Specifically, the volume and hardness of the filler is increased, and the number of carcass plies is increased.

However, the above (1) and (4) increase the weight of the tire and increase the cost), which is unfavorable in terms of tire performance, and increases the pressure when fitting the tire to the rim, which is undesirable in terms of mounting on the rim. isn't it. Similarly, (3) is not preferable because it becomes difficult to fit the tire onto the rim unless the fitting pressure is increased.

Therefore, it can be seen that (2) above is advantageous in order to maintain the original tire performance without increasing the tire weight or cost, and to obtain a tire that is difficult to come off the rim.

The present inventors have carried out extensive studies based on the above knowledge and have arrived at the present invention.

[Problem to be solved by the invention]

As described above, an object of the present invention is to provide a tire that has excellent rim detachment prevention performance without increasing the weight or cost of the tire and without impairing tire performance.

[Means to solve the problem]

In the present invention, the ratio (βI/W) of the tire axial distance It between the cross-sectional center position of the bead core and the bead toe to the full width W of the bead bottom of the tire exceeds 0.5 and 0.
It is characterized by being 6 or less.

Here, W is the distance in the tire axial direction between the bead toe 6 and a point Q (Fig. 1) where a line extending from the center of gravity of the bead core in the tire axial direction intersects with the tire outer wall on the heel 7 side of the tire bead, lI is the distance in the tire axial direction between the cross-sectional gravity center position of the bead core and the bead tow 6.

FIG. 1 is a partial sectional view showing an example of a bead portion of the tire of the present invention.

As shown in the figure, in the bead portion, a carcass layer 4 is wound around a bead core 3 made of stainless steel wire or the like, and the inside of the wound carcass layer 4 is filled with a filler 5 such as rubber, and the outside of the carcass IW 4 is filled with a filler 5 such as rubber. An inner liner bead toe 6, bead heel 7, rim cushion 8, etc. are formed on the inner liner.

In normal tires, the ratio (ll/W) of the distance 11 in the tire axial direction between the cross-sectional center of gravity of the bead core and the bead toe to the total width W at the bottom of the bead portion is usually 0.5 or less. .

The present invention has the above ratio (β, /W) exceeding 0.5 and 0.6
The following shall apply.

As a specific means for making the above ratio (l l/W) more than 0.5, since W is determined by the bead ring shape of the mold and usually cannot be changed, the thickness of the rim compression (rubber layer) 8 is A method for making the ratio (ll/W) more than 0.5 by making it thinner is adopted.

Generally, the rim traction layer 8 is provided at a portion that comes into contact with the rim flange, and has the function of protecting the carcass layer from damage caused by rubbing against the rim. /W) to 0
．． It has a rating of over 5, which improves the ability to prevent the tire from coming off the rim. Surprisingly, according to an experiment conducted by the present inventors on power transformation, even if the thickness of the rim traction (rubber layer) 8 is made thinner, in the case of the tire of the present invention, the function of the rim traction 8 is not impaired. confirmed.

This is because the rim traction 8, which is in a position where it comes into contact with the rim flange and undergoes compression deformation, rubs against the rim in two ways: rubbing in the tire circumferential direction and rubbing in the tire radial direction. It turned out that this function was to prevent damage from rubbing in the radial direction. Therefore, it can be said that if the movement of the rim cushion 8 in the tire radial direction is reduced, the anti-rubbing function required of the rim cushion can also be reduced.

According to the present invention, by setting the ratio (β1/W) to more than 0.5, the moment around the bead toe increases, and the lifting of the bead portion due to the same lateral force becomes smaller (the force for radial tightening is , caused by deformation of the bead tow). Therefore, even if the rim cushion is thin, the degree of rubbing damage to the carcass layer is almost the same as in the conventional case.

However, if the ratio (x+/W) is too large, it is not preferable in terms of preventing rim displacement in the tire circumferential direction.

That is, for the bottom part of a tire, especially a tire for a passenger car, a member that is highly elastic and easily deformable is used in order to ensure sufficient tightening force and air sealing properties. As shown in Fig. 5, from the viewpoint of deformation (rim compression) to the rim shape, the rim taper (the angle formed by the extension line of the rim bead seat and the rotational axis of the tire) is set to 5°, and the rim taper is adjusted to correspond to this rim taper. By making the taper at the bottom of the bead part (the angle formed by the tire bead toe extension line and the rim bead seat extension line) substantially 3° to 10°, the compression on the bead toe 6 side is the same as that of the bead heel 7 cases. When assembling the tire rim, it is common to make it larger and generate a large tightening force closer to the bead toe in consideration of ease of rim assembly and air sealing properties.

〔Example〕

By changing the cross-sectional center of gravity position of the tire bead core, the ratio (l
5 types of tires (tire size 185) with different l/W)
/70R13) Prepare a total of 10 tires, 2 each, and install the same specification tires on the front wheels to achieve a speed of 0.8G from 80Km/hr.
As a result of measuring the amount of rim deviation (open) after repeating the brake test five times, as shown in Figure 3, the ratio (#I/
When W) is 0.6, the average amount of rim deviation of the tires mounted on the left and right front wheels is about 5 mm, but when it exceeds this, it was confirmed that the amount of rim deviation increases rapidly. This is because tightening force using a bead core is reduced. therefore,
The value of this ratio (11/W) has a limit of 0.6, and it is not preferable to exceed this value.

On the other hand, four types of tires A, B, C, and D, different from the above example in which the ratio (1+/w) was changed, were prepared, and a lateral push load was applied to them, and the air pressure was determined based on the rim removal air pressure. We investigated the leak situation.

Here, the tire size is 185/70SR13, the rim used is 5J x 13, and each tire is 3
The rim release air pressure when applying a lateral push load in stages was measured twice each, and the results are shown in a table, and the average value of these measured values is plotted in FIG. 4.

The lateral push load in the above three stages is 500Kgf, 700Kg
f and 900 Kgf, but the load during the test was actually the value shown in parentheses ().

Here, when the lateral push load exceeds 750Kgf, 1.
Judgment is made by comparing the air leak test results with the indoor side-push air leak test standard, which states that if the tire does not come off the rim at an air pressure of 3 kg/cm, it is considered "pass", and if it does, it is "fail". , shown in the table.

As shown in the table, Tire A did not meet the air leak test standards, and all other tires B, C, and D did.

Therefore, a tire with a ratio (j'l/W) of more than 0.5 has a lateral push that causes the rim to come off at the same air pressure, compared to a tire A with a ratio (tt +/W) of 0.45. The load increased by about 50 kgf or more, and excellent rim detachment prevention performance was observed.

〔Effect of the invention〕

In the tire of the present invention, the cross-sectional center of gravity of the bead core (wire) is determined by the tire bead width W, the distance in the tire axial direction between the bead core's cross-sectional center of gravity and the bead toe. Arrange so that the ratio (Jl/W) is within a certain range (
By separating the tire from the bead toe (compared to conventional tires), the rim's ability to prevent the rim from coming off is improved and driving safety is ensured without impairing tire performance.

5... Bead filler layer, 6... Bead tow, 7.
...Bead heel, 8...Limbushion.

Claims (1)

[Claims] Distance l in the tire axial direction between the cross-sectional center of gravity of the bead core and the bead toe with respect to the full width W of the bottom of the bead of the tire
A pneumatic radial tire in which the ratio of _1 (l_1/W) is more than 0.5 and less than 0.6.